Chapter 131. Diphtheria and Other Infections Caused by Corynebacteria and Related Species (Part 5) docx

Chapter 131. Diphtheria and Other Infections Caused by
Corynebacteria and Related Species
(Part 5)

Management
Patients in whom diphtheria is suspected should be hospitalized in
respiratory isolation rooms, with close monitoring of cardiac and respiratory
function. A cardiac workup is recommended to assess the possibility of
myocarditis. In patients with extensive pseudomembranes, consultation with an
anesthesiologist or an ear, nose, and throat specialist is recommended because of
the possibility that tracheostomy or intubation will be required. In some settings,
pseudomembranes can be removed surgically. Treatment with glucocorticoids has
not been shown to reduce the risk of myocarditis or polyneuropathy.
Prognosis
Fatal pseudomembranous diphtheria typically occurs in patients with
nonprotective antibody titers and in unimmunized patients. The pseudomembrane
may increase in size from the time it is first noted. Risk factors for death include
bullneck diphtheria; myocarditis with ventricular tachycardia; atrial fibrillation;
complete heart block; an age of >60 years or <6 months; alcoholism; extensive
pseudomembrane elongation; and laryngeal, tracheal, or bronchial involvement.
Another important predictor of fatal outcome is the interval between local disease
development and antitoxin administration. Cutaneous diphtheria has a low
mortality rate and is rarely associated with myocarditis or peripheral neuropathy.

Prevention
Vaccination
Sustained campaigns for vaccination of children and adequate boosting
vaccination of adults are responsible for the exceedingly low incidence of
diphtheria in most developed nations. At present, diphtheria toxoid vaccine is
coadministered with tetanus (with or without acellular pertussis) vaccine. DTaP
(full-level diphtheria and tetanus toxoids and acellular pertussis vaccine, adsorbed)

is the currently recommended vaccine for children up to the age of 7; DTaP
replaced DTP (diphtheria and tetanus toxoids and whole-cell pertussis vaccine) in
1997. Tdap is a tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis
vaccine formulated for adolescents and adults. Tdap was licensed for use in the
United States in 2005 and is the recommended booster vaccine for children 11–12
years old and the recommended catch-up vaccine for children 7–10 and 13–18
years old. As of 2006, it is recommended that (1) adults 19–64 years old receive a
single dose of Tdap if their last dose of Td (tetanus and reduced-dose diphtheria
toxoids, adsorbed) was >10 years earlier and (2) intervals of <10 years be
implemented for Tdap vaccination of health care workers, adults anticipating
contact with infants, and adults not previously vaccinated for pertussis. Adults
who have received acellular pertussis vaccines should continue to receive
decennial Td booster vaccinations. The vaccination schedule is detailed in Chap.
116.
Prophylaxis of Contacts
Close contacts of diphtheria cases should undergo throat culture to
determine whether they are carriers. After samples for throat culture are obtained,
antimicrobial prophylaxis should be considered for all close contacts, even those
who are culture-negative. The options are 7–10 days of oral erythromycin or one
dose of IM benzathine penicillin G (1.2 million units for persons ≥6 years old or
600,000 units for children <6 years old).
Contacts of diphtheria cases who have an uncertain immunization status
should receive the appropriate diphtheria toxoid–containing vaccine. Tdap (rather
than Td) is now recommended as the booster vaccine of choice for adults who
have not recently received an acellular pertussis–containing vaccine. Carriers of C.
diphtheriae in the community should be treated and vaccinated when identified.
Nondiphtherial Corynebacteria and Related Species
Nondiphtherial corynebacteria, which are also referred to as diphtheroids or
coryneforms, are a widely diverse collection of bacteria that are taxonomically
lumped together on the basis of their 16S rDNA signature nucleotides. The

diversity of this group is exemplified by the wide range in guanine-plus-cytosine
content (45–70%). Although frequently considered colonizers or contaminants, the
nondiphtherial corynebacteria have been associated with invasive disease,
particularly in immunocompromised patients. Specifically, for example, these
organisms have been implicated in bacteremia, particularly in association with
catheterization, endocarditis, prosthetic valve infection, meningitis, neurosurgical
shunt infection, brain abscess, peritonitis (often in the setting of chronic
ambulatory peritoneal dialysis), osteomyelitis, septic arthritis, urinary tract
infection, empyema, and pneumonia. Patients infected with nondiphtherial
corynebacteria usually have significant medical comorbidity or
immunosuppression. Several of these organisms, including C. jeikeium and C.
urealyticum, are associated with resistance to multiple antibiotics. The related
organism Rhodococcus equi is associated with necrotizing pneumonia and
granulomatous infection, particularly in immunocompromised individuals. Other
related species that can cause infections in humans are Actinomyces (formerly
Corynebacterium) pyogenes and Arcanobacterium (formerly Corynebacterium)
haemolyticum.